Hoist pushbutton control



Sept. 23, 1969 J. P. TRU-EMPER FT Aly 3,469,164

HOIST FUSHBUTTON CONTROL med Feb. 4. 196e l 44) CIRCUITS INVENTORs J. l?TRUEMPER .F.zg. .5' ATTORNEYS Unified Patent ULS. Cl. 318-257 3 ClaimsABSTRACT OF THE DISCLOSURE In this electric hoist control there areutilized a lifting control pushbutton and a lowering control pushbuttonmounted for depressing movement on one side of a housing,- as is ratherusual. With those buttons, there-is an interlock cammounted for slidingon the control housing andvmoved by each pushbutton during a first partof its depressing `movement so as to lock the other button in neutralposition. A switch is moved by the interlock cam so as to actuate adirectional control circuit when the cam is moved by either button. Eachpushbutton has a stem connected to a movable core of a` variabletransformer that forms a part of a speed control circuit. The switchhaving actuated a directional circuit, further depressing movement ofthe button will vary the current in the speed circuit.

Our invention relates to a novel pushbutton operated control that isparticularly adapted for controlling speed and direction circuits on avariable speed hoist.

Those persons skilled in the art will appreciate that hoists frequentlyare equipped with pushbuttons that an operator will utilize to controlthe lifting'and lowering movements of the hoist. Many people prefer apush button control because such controls are simple to operate and mayvery readily be connected to a hoist through a flexible cable, so as tobe convenient for the operator to use while he directs his attention toa load being handled by the hoist. Ihe novel push button control that wecontribute by our invention is particularly adapted to actuate speed anddirection circuits on a hoist, and will enable the operator to haveextremely effective control over the movements of the hoist.

In the form of our novel control that We prefer, we utilize a pair ofpushbuttons, one being a lifting control button and the other avlowering control button, each adapted to be depressed through aconsiderable control distance. During a first part of its depressingmovement, each pushbutton will `rnove a switch to -a correspondingdirection control position. Further depressing movement of thepushbutton will operate a variable current regulating device that isadapted to control a speed circuit on the hoist, but the' switch willnot move beyond the control positonin which it was first placed by thebutton.

Thus, as a feature of our novel pushbutton control, we utilize a switchthat a pushbutton will operate to control the direction in which thehoist moves, but that will have no contacts that need slide while the'pushbutton moves to operate a variable speed control device.

As a more detailed feature, We Operate a direction control switchthrough interlocking means that will lock one of two pushbuttons in a'neutral position when the other pushbutton is depressed. When furtherdepressed, theq button that is not lockedr will operate a variabledevice while the interlocking means merely' hold the direction controlswitch in a particular Voperated position.

As a further feature, we prefer to utilize as a part of our novelpushbutton control, a variable current regulating device that willcontribute infinite speed control while requiring no sliding'contacts.That device may be a variice able transformer that is so connected to apushbutton as to vary its current output as the button is depressed. Thepushbutton first will actuate a switch that will control the directionin which the speed control is applied.

We lhave thus outlined rather broadly the more important features of ourinvention in order that the detailed description thereof that followsmay be better understood, and in order that our contribution to the artmay be better appreciated. There are, of course, additional features ofour invention that will be described hereinafter and which will form thesubject of the claims appended hereto. Those skilled in the art willappreciate that the conception on which our disclosure is based mayreadily be utilized as a basis for the designing of other structures forcarrying out the several purposes of our invention. It is important,therefore, that the claims be regarded as including such equivalentconstructions as do not depart from the spirit and scope of ourinvention, in order to prevent the appropriation of our invention bythose skilled in the art.

In the drawing:

FIGURE l shows an electric hoist that is equipped with our novelpushbutton operated control.

FIGURE 2 shows a cross-section of our control, taken on the line 2-2i11FIGURE 3.

FIGURE 3 is a longitudinal section showing parts of our invention.

FIGURE 4 shows diagrammatically how our control may be utilized.

Referring now more particularly to FIGURE 1 of the drawing, we show ournovel ibushbutton control 10 connected through a exible cable 11 to anelectric hoist 12 of a usual type. The hoist 12 has a motor 13 that willoperate a drum 14 so as to wind va rope 15 on which is a load hook 16',and there is a suspension hook 17 through which the hoist 12 issupported. Portions 18, 19

of the hoist housing enclose parts of the motor control circuits and thehoist mechanism, not shown. Further details of the hoist 12 are notimportant to an understanding of our invention, and it is merelynecessary to know here that our novel pushbutton control 10 will actthrough wires in the fiexible cable 11 to operate motor control circuitson the hoist 12.

The novel control 10 of our invention includes a pair of pushbuttons 20,21, well shown in FIGURE 3, having stems 22, 23 that are mounted toslide in openings in a casing 24. A coil spring 25 presses each button20, 21 in an outward direction, normally holding the button in a neutralposition in which a lug 26 on each stem 22, 23 is against an innersurface of casing 24.

Referring to FIGURE 3, an interlock cam 27 is mounted for slidingmovement in openings that are formed in transverse wall portions 28 onthe casing 24, the cam 27 having tapered end portions 29 for coactingwith surfaces on the pushbutton stems 22, 23. The cam ends 29 are soformed that each pushbutton 20, 21 will act during a first part of itsdepressing movement to slide interlock cam 27 in one direction or theother, causing the cam to lock the other pushbutton in neutral position.The pushbutton that slides the cam can be further depressed through aconsiderable distance, but when so depressed will cause no furthermovement of cam 27 because a side surface of the button stem will merelyhold the cam in locking position.

Our control further includes a three-position switch 30, FIGURE 3, thatwill be operated by the interlock cam 27. As shown, switch 30 is mountedbetween the wall portions 28 on casing 24, and has a spring contactfinger 31 engaging a recess in the cam 27. At opposed sides of contactfinger 31, the Wsitch 30 has further contact fingers 32, 33. Normally,the first contact finger 31 will be in open circuit relation to fingers32, 33, and will act by its spring pressure to hold interlock cam 27 inneutral position. When cam 27 slides due to a depressing movement ofeither pushbutton 20, 21, that cam will move the contact finger 31 intocircuit closing position relatively to a corresponding finger 33 or 32.It will thus be seen that interlock cam 27 upon moving to lock apushbutton will be effective for closing a particular circuit. Also,once the cam 27 has placed switch 30 in position closing a circuit, theswitch will remain in that position and will have no further movementwhen there is a further depressing movement of the pushbutton that hasmoved cam 27.

We prefer to utilize a pair of variable transformers 34, 35 that aremounted within the casing 24, as -by screw studs 36 extending throughopenings in a wall of the casing and held by nuts 37. Each transformer34, 35 has an axially extending core opening 38 that is in alignedrelation to a corresponding pushbutton 20, 21. While not seen in FIGURE3, each transformer 34, 35 includes a primary winding 39 and a secondarywinding 40 as shown diagrammatically in FIGURE 4. On each pushbuttonstem 22, 23 is a slug 41 that forms a movable core for the correspondingtransformer 34, 35. The primary winding 39 of each transformer 34, 35will be energized by a suitable source of power, and the secondaryoutput of each transformer naturally will increase as a pushbutton movesits slug or core 41 farther into the core opening 38, as will beunderstood by those skilled in the art. For purposes of adjustment, eachcore 41 is attached to its pushbutton stem through a screw member 42 onwhich the core can be rotated to change its longitudinal positionrelatively to the stem. To facilitate that adjustment, the casing 24 isformed with openings 43 through which a tool may be inserted intoengagement with a slot 43a in either core 41.

The arrangement is such that each transformer 34, 35 will produce anoutput that is at a minimum while the corresponding pushbutton 20, 21 isin neutral position and until that button has been depressedsufficiently to cause switch 30 to actuate a circuit. However, sincetransformer cores 41 can be adjusted on the screw members 42, it will bepossible to set as may be desired the amount of transformer output thatwill be effective at the time when switch 30I closes a circuit.

We believe it will now be clear that the switch 30 of our novel controlmay very well be utilized for actuating alternately a lifting controlcircuit and a lowering control circuit for a hoist motor. Once a liftingor lowering circuit is actuated, each transformer 34, 35 may beeffective for applying infinite speed control to a motor speed circuitthat is responsive to a varying current. To illustrate better the mannerin which our control may be used, we have shown the circuitsdiagrammatically in FIGURE 4. Of course, there will be a suitable sourceof power 44 that will energize the transformer primary windings 39. Thesecondary winding 40 of each transformer 34, 35 will be connected to aspeed control circuit 45 for the hoist motor 13, and switch 30 will beconnected to lifting and lowering control circuits 46. When the hoistoperator wishes to operate the hoist in lifting direction he merely needdepress the proper pushbutton, which we may assume is the button 20. Aswe have already indicated, a first part of the depressing movement oflifting control button 20 will slide the interlock cam 27 so as to lockthe lowering control button 21 in neutral position, while also causingswitch 30 to actuate lifting control circuit 46. When the operatorfurther depresses the button 20, the speed control circuit 45 willeffect operation of the hoist motor 13 in the lifting direction and at aspeed corresponding to the distance through which button 20 isdepressed.

Thus far we have not referred to the particular mounting of controlcasing 24, but it will be seen in FIGURES 2 and 3 that casing 24 may besecured through screws 50 to a bracket 51 and a plate 52, that extendabout the pushbutton stems 22, 23 and the springs 25. The plate 52 mayin turn be secured through screws 53, FIGURE 2, to a portion 54 of anouter housing that is indicated generally by the numeral 55. Housingportion 54 has openings for pushbuttons 20, 21, and a flexible gasket 56extends between plate 52 and buttons 20, 21 to protect the interior ofour control against the entrance of dirt. In one construction that wemay use, the housing portion 54 will be secured by suitable means to ahousing portion 57 that is formed with a tubular extension 58 to whichthe flexible control cable 11 is attached. As will be understood,the-cable 11 includes a series of wires, some of which are indicated at59, extending from the windings of transformers 34, 35 and the fingersof switch 30 to the control circuits 45, 46 and source of power 44 onthe hoist 12. FIGURE 2 further shows a wire 60 `supporting a strainrelief bracket 61 that engages the housing portion 57.

The novel pushbutton control of our invention will enable the operatorof a variable speed hoist to have extremely effective control over theoperation of the hoist motor. The operator actually may apply infinitespeed control, and the pushbuttons will be interlocked so that thereneed be no relay or other additional means to prevent conflictingoperation of the control circuits. It is important to realize that ourvariable speed control will require no sliding electric contacts of anykind, and that it will need little or no attention for repairs after itis placed in use. While achieving these things, we are able neverthelessto make our control quite small, and it actually is possible to installour control in standard pushbutton control housings that are in usetoday. We believe, therefore, that the very considerable value of ournovel pushbutton control will be understood, and that the merits of ourinvention will be fully appreciated by those persons who are skilled inthe art.

We now claim:

1. In a pushbutton operated control for an electric hoist, said controlhaving a housing, a lifting control pushbutton -and a lowering controlpushbutton individually mounted for depressing movement relatively to aparticular side of the housing, each pushbutton having a stem moving ina linear direction in the housing when the button is depressed from aneutral position, the improvement that comprises interlocking meansmoved by each pushbutton stem during a first part of the depressingmovement of its button whereby to lock the opposed button in neutralposition, in combination with a plurality of electric current regulatingdevices each operable for effecting a varying current control, each ofthe pushbutton stems being connected to a separate one of said currentregulating devices so as to operate that device while the correspondingpushbutton is depressed varying distances, a switch having contactsnormally in a neutral position and movable to an actuated position, anda portion of said interlocking means coacting with said switch to moveits contacts to actuated position when said interlocking means move tolock a pushbutton.

2. A construction as set forth in claim 1, in which each currentregulating device is a variable transformer mounted on said housing landhaving a core connected to a pushbutton stem so as to be moved by apushbutton for varying the output of said transformer.

3. A construction as set forth in claim 1 in which said interlockingmeans include an interlock cam mounted to slide in a transversedirection on the housing, a surface on one pushbutton stem coacting withan end of said cam for sliding said cam, and said switch including aseries of contact fingers one of which engages said cam, so that saidcam will move said one contact finger alternately into contact with eachof two other fingers when alternate pushbuttons are depressed.

(References on following page) 5 6 References Cited ORIS L. RADER,Primary Examiner UNITED STATES PATENTS K. L. CROSSON, Assistant Examiner2,572,295 5/ 1951 Ziegler S18-344 -X 3,312,122 4/1967 Conner et al. S35-16o U'S' C1' XR' 3,313,877 4/1967 Boenning 323-51 5 317--157.6; S18-344;323-51; 336-105

